CMC will miss Week 18 against. Rams with slight right calf strain.

Coach Kyle Shanahan must consider a lot this week as the 49ers prepare for their Week 18 matchup against the Rams.

With their 27-10 win over the Washington Commanders at FedExField on Sunday and the Philadelphia Eagles' defeat to the Arizona Cardinals, the 49ers secured the NFC's top playoff spot.

While sitting all their top players is tempting, it's impossible. However, running back Christian McCaffrey will miss the season finale due to a moderate right calf injury.

Shanahan predicted McCaffrey will be ready for the 49ers' first playoff game on Jan. 20 or 21. “We’re real confident on that,” Shanahan told Bay Area reporters Monday during a conference call. “Good news. It might have been far worse. We're glad. We'll watch him this week and perhaps he'll start going during our off week.”

The calf injury restricted McCaffrey to one carry in the second half of Sunday's game. Elijah Mitchell, a backup, ran for 80 yards and a touchdown on 17 carries. Shanahan wasn't sure whether Brock Purdy would play against the Rams. After two stingers, he played Sunday without any concerns.

The 49ers can have seven inactive players, including cornerback Ambry Thomas. Broken hand surgery is scheduled for Tuesday for Thomas. He should be available for the 49ers in the playoffs.

Foot and knee injury will keep defensive lineman Arik Armstead out of the Rams game. His absence spans four games. Armstead will be rested and prepared for the playoffs, Shanahan said.

Safety Ji'Ayir Brown (knee) and Ross Dwelley (high ankle) may miss the Rams game. Both wide receiver Jauan Jennings and backup lineman Jaylon Moore are in the NFL's return-to-play concussion protocol.

Ray-Ray McCloud (ribs) will report to practice on Wednesday for the 49ers. McCloud and Danny Gray (shoulder) may be activated this week. Gray's first practice week was last week.

Watch this space for further developments.